As an example of a resistance change memory, a phase change memory is an element that uses a property of transitioning between an amorphous state and a crystalline state by adding heat electrically generated to a chalcogenide type material (Ge, Sb, Te), to perform storage. In a cell formed by a phase change memory, in a case of starting a phase change by Joule heat by electrical current to perform writing, as shown in FIG. 10, when there is a transition from a low resistance state (set state, crystalline state) to a high resistance state (reset state, amorphous state), a large current is flowed for a short time. Conversely in a case of transitioning from a high resistance state (reset state, amorphous state) to a low resistance state (set state, crystalline state), it is necessary to flow a comparatively low current for a long time. In this regard, in a case of performing reading, as shown in FIG. 10, it is sufficient to flow a smaller current compared to a case of writing.
A phase change memory device performing writing and reading as described above is disclosed in Patent Document 1. This phase change memory device is provided with a phase change memory that includes a plurality of memory cells; a write step-up circuit that, in a first operation mode (a write operation mode), responds to a control signal (a write active signal) to step-up a first voltage (power supply voltage), to be outputted as a first control voltage (a voltage that is sufficiently high in order to start a phase change in a selected memory cell), and in a second operation mode (a read operation mode) or a third operation mode (standby mode), responds to a control signal to step-up the first voltage, to be outputted as a second control voltage (a voltage that is lower than the first control voltage, and higher than the first voltage); and a write driver that, in the first operation mode, is driven by the first control voltage and writes data to the selected memory cell. It is to be noted that, as the step-up circuit, a charge pump circuit using a capacitive element is generally used.    [Patent Document 1]    JP Patent Kokai (laid-open) Publication No. JP-P2007-26644A